The tree with the golden sap
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CTA. 1990. The tree with the golden sap. Spore 25. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/45205
Acacia senegal, which produces gum arabic, has suffered greatly from the effects of the drought. This tree with the golden sap (gum arabic) does not thrive in plantations, so the only viable method of restoring it to previous numbers is to protect...
Acacia senegal, which produces gum arabic, has suffered greatly from the effects of the drought. This tree with the golden sap (gum arabic) does not thrive in plantations, so the only viable method of restoring it to previous numbers is to protect its natural environment. Trees in the Sahel have a variety of ways of resisting the vagaries of the climate. Acacia tortilis delays blooming until the last rains because the onset of the cool season fluctuates so much. The baobab keeps its reserves of water inside its trunk. Most species have developed huge root systems which can seek water as far away as possible. But the Acacia senegal, has perhaps the most interesting drought defence system of all: to avoid dehydration when the wind, animals or insects damage its trunk, it secretes a viscous liquid known as gum arable. Gum arabic- a rare and precious commodity Man has long harvested gum arabic as something rare and precious. In ancient fumes it had considerable commercial value and this has not diminished. Its rarity comes from the fact that only the gum tree produces it, and a satisfactory substitute has never been found. It is used for glue, sweets, pills and lozenges; it stabilizes wine and fizzy drinks; it is a fixative for paintings and ceramics; and local people use it for starching their traditional costumes, for cooking, and for medicine. Over the years, the tapping of the trees for gum has developed into a skilled operational In Mauritania, northern Senegal, Niger and Mali all the stockmen, from the Moors to the Peulhs, shepherds and nomads, collect the gum when they go in search of new pastures for their flocks and herds. Some even take their cattle to those areas where there are gum trees to tap because they know they can sell what they get as additional income. A small tree well adapted During the drought years of the Seventies, the Sahelian landscape lost many gum trees, despite the fact that this five-six metre tree with its low thorny bushy branches is well suited to the Sahelian climatic conditions. It needs only about 250-270mm rainfall, and can withstand nine to eleven months of drought and temperatures of 45C. Its rough thick bark protects it from this heat. Its main roots can descend one metre, and its secondaries are long and supple and can spread out through the sand so the strong Harmattan winds cannot uproot the tree. However, the disappearance of the gum tree is more the result of disarry in herd movements than of the drought. Herdsmen lead their stock into the least arid areas, but that is precisely where the gum tree is most likely to flourish again and young shoots get eaten and the trees destroyed. Nomads have not yet gone back to their old routes and they need to graze their herds and flocks where they are at present but the gum tree is specially enjoyed by goats, cattle, and - above all - camels. As a result the production of gum declined sharply, from 60,000 tonnes in 1970 to 20,000 tonnes in 1980, and has now stabilized around 45, 000 tonnes Large-scale plantations There have been various attempts to domesticate this tree, but large plantations have not been successful Acacia senegal plantation, principally in Mali have had variable results: some trees produce gum well (between five and ten kilo per annum) but others produce only one kilo. Scientists have not yet managed to isolate, and then reproduce, the most productive strains. Research programmes are in train but no results will be published for some years. Meanwhile the best means of preserving this useful tree is still to protect it from the ravages of man, beast and fire where it occurs naturally.